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Basal area is the cross-sectional area of trees at breast height (1.3m or 4.5 ft above ground). It is a common way to describe stand density. In forest management, basal area usually refers to merchantable timber and is given on a per hectare or per acre basis. If one cut down all the merchantable trees on an acre at 4.5 feet (1.4 m) off the ...
Borderline trees occur only when the distance from the sampling point to the center of the tree is equal to the DBH times plot radius factor (PRF). The PRF is determined based on the type of prism or angle gauge being used. Basal Area Factor (BAF) 5, 10, and 20 angle gauges result in PRFs of 3.89, 2.75, and 1.94 (feet inch −1) respectively.
The above equation is an expression for computing the stand density index from the number of trees per acre and the diameter of the tree of average basal area. Assume that a stand with basal area of 150 square feet (14 m 2) and 400 trees per acre is measured. The dbh of the tree of average basal area D is: = Substituting this value into the ...
Basal area is estimated by multiplying the count of "in" trees at a given point by the 'factor' of the prism. Prism factor is based on the angle of the prism, and prisms are available in different factors, expressed in both square feet/acre (5, 10, 20 BAF are most common) and square meters/hectare (1-5 BAF are common).
When stocking, a tree's basal area is measured. The basal area is a cross-sectional area of the stump taken about 4.5 feet (1.4 m) above the ground. [7] The equation for calculating the basal area of trees in a stand is Basal Area = 0.005454 DBH 2, where DBH is the diameter of the tree at the aforementioned measuring height. [7]
Proper use of angle gauge to count in trees Angle gauge indicating a tree to measure for a basal area factor of 10. An angle gauge is a tool used by foresters to determine which trees to measure when using a variable radius plot design in forest inventory. Using this tool a forester can quickly measure the trees that are in or out of the plot.
The Relascope is very similar to the angle gauge and the wedge prism in that it can be used to find the basal area of a tree from a point depending on the basal area factor in a variable radius sampling method. The main difference in this instrument though is that it has multiple uses as described previously.
The value 75.4 = 24 π, where 24 π substitutes for factor of 12 π in the formula for a volume of frustum of a cone encompassing a full tree using one base circumference, converting it to a volume formula that uses a basal circumference that is the average of circumferences C 1 and C 2.